Frame Sway Cylinder - JLG sky trak mmv Service Manual

Hydraulic System
g. Lift/Lower Cylinder Pressure Checking and
Circuit Bleeding
1. Attach a 5000 psi (345 bar) gauge to the main control
valve at the extend/retract base port relief to test the
lift/lower cylinder hydraulic system circuit pressure.
The unit is equipped with test fittings from the
factory. Pressure readings should be 3750 ±100 psi
(259 ±7 bar). Refer to Section 9.7, Hydraulic System
Testing .
2. With no accessory installed on the quick attach, start
with the lift/lower and attachment tilt cylinders fully
retracted.
3. Fully raise and fully extend the boom. Hold the
joystick at full extend while fully raising the lift/lower
cylinder.
4. Fully retract the attachment tilt cylinder. Hold the
joystick at full retract while fully lowering the boom.
5. Repeat Steps 3-4 five times.
9.14.8

Frame Sway Cylinder

The frame sway cylinder (1) is attached to the right side
of the frame at the front axle and to the cast loop on the
axle.
1
a. Frame Sway Cylinder Removal
1. Park the vehicle on a firm, level surface, fully retract
all hydraulic cylinders, ground the attachment (if
any), place the travel select lever in [N] NEUTRAL,
place the neutral lock lever in the [N] NEUTRAL LOCK
position, engage the park brake switch and shut the
engine OFF.
2. Place an Accident Prevention Tag on both the
ignition switch and the steering wheel, stating that
the vehicle should not be operated. Refer to Section
1.5, Accident Prevention Tag Usage .
WARNING:
cause severe burns. Wait for hydraulic fluid to
cool before servicing any hydraulic component.
3. Unlatch and open the engine cover. Allow the
hydraulic fluid to cool.
9.160
MM3810
Hot hydraulic fluid can
WARNING:
under pressure can penetrate the skin, causing
death or serious injury. Relieve hydraulic
pressure before servicing any hydraulic
component.
4. Label or otherwise mark the hydraulic hoses in
relation to the cylinder being removed. Safely
position suitable supports between the frame and
axle to prevent the frame from leaning to one side.
5. Disconnect and cap all hoses and fittings, etc.
6. Use a sling and hoist or other suitable lifting device
to support the cylinder. Remove the nuts,
capscrews, and cylinder mount pins securing the
cylinder to the frame and anchor plate.
7. Remove the cylinder from the vehicle. Wipe up any
hydraulic fluid spillage in, on, near and around the
vehicle.
b. Frame Sway Cylinder Disassembly
Note: An additional o-ring may be included at the base
of the cylinder rod. This additional o-ring may be dis-
carded, as it served only in a temporarily protective role.
1. Clean the frame sway cylinder (2) with a suitable
cleaner. Remove all dirt, debris and grease from the
cylinder.
IMPORTANT: Avoid using excess force when clamping
the cylinder in a vise. Apply only enough force to hold the
cylinder securely. Excessive force can damage the
cylinder.
2. Secure the frame sway cylinder (2) in a soft-jawed
vise or other holding device, and place a suitable
container beneath the cylinder to catch hydraulic
fluid run-off.
WARNING:
may be trapped inside the cylinder. Exercise
caution when removing a counterbalance valve
or a pilot-operated check valve from a cylinder.
Escaping hydraulic fluid under pressure can
penetrate the skin, causing death or serious
injury.
3. Slowly remove the pilot-operated check valves (3)
from the frame sway cylinder.
Escaping hydraulic fluid
Significant pressure
Model MMV Rev. 12/04